Conventionally, sheet glass has almost always referred to glass having a thickness equal to or smaller than 10 millimeters (mm). Recently, however, thick sheet glass having a thickness larger than 10 mm and closer up to 25 mm has been used more frequently as sheet glass used for buildings. Following the frequent use of the thick sheet glass, need arises to cut such thick sheet glass into pieces of optimum sizes for each building. Accordingly, a breaker is desired so that a cut surface of sheet glass of any type including thick sheet glass is smooth and so as to be able to cut the sheet glass as easily as possible.
As a conventional manual breaker cutting sheet glass using so-called three-point bending, manual breakers disclosed in, for example, Patent Documents 1 and 2 are known. The manual breaker of the Patent Document 1 is a glass breaker for cutting thick sheet glass into pieces. According to the Patent Document 1, a lifting drive mechanism is provided at a lower position between two fixed support anvils and a movable pressurizing element is provided in an upper portion of this lifting drive mechanism. The lifting drive mechanism lifts up the movable pressurizing element, thereby moving sheet glass so as that the sheet glass adjoins the fixed support anvils. At this time, the two fixed support anvils and the movable pressurizing element pinch the sheet glass among them to create a state of three-point bending. Accordingly, if the lifting drive mechanism further lifts up the movable pressurizing element, the sheet glass is cut into pieces.
The manual breaker of the Patent Document 2 is a glass breaker for cutting sheet glass into pieces. This glass breaker is configured so that two holding elements are held in a width adjustment frame that is an upper frame, and so that a pressurizing element is held in a lower frame to face the two holding elements. Sheet glass is pinched among three points, that is, the two holding elements and the pressurizing element to create a state of three-point bending and a force of pinching the sheet glass is strengthened to thereby cut the sheet glass into pieces.
Patent Document 1: Japanese Unexamined Patent Publication No. 11-228162
Patent Document 2: Japanese Utility Model Registration No. 3056772.